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mount

MOUNT(8)                   Linux Programmer's Manual                  MOUNT(8)



NAME
       mount - mount a file system

SYNOPSIS
       mount [-lhV]

       mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
       mount [-fnrsvw] [-o options [,...]] device | dir
       mount [-fnrsvw] [-t vfstype] [-o options] device dir

DESCRIPTION
       All files accessible in a Unix system are arranged in one big tree, the
       file hierarchy, rooted at /.  These files can be spread out  over  sev-
       eral  devices. The mount command serves to attach the file system found
       on some device to the big file tree. Conversely, the umount(8)  command
       will detach it again.

       The standard form of the mount command, is
              mount -t type device dir
       This  tells the kernel to attach the file system found on device (which
       is of type type) at the directory dir.  The previous contents (if  any)
       and  owner  and  mode of dir become invisible, and as long as this file
       system remains mounted, the pathname dir refers to the root of the file
       system on device.

       Three forms of invocation do not actually mount anything:
              mount -h
       prints a help message;
              mount -V
       prints a version string; and just
              mount [-l] [-t type]
       lists  all mounted file systems (of type type).  The option -l adds the
       (ext2, ext3 and XFS) labels in this listing.  See below.

       Since Linux 2.4.0 it is possible to remount part of the file  hierarchy
       somewhere else. The call is
              mount --bind olddir newdir
       After this call the same contents is accessible in two places.

       This  call  attaches  only  (part of) a single filesystem, not possible
       submounts. The entire file hierarchy including submounts is attached  a
       second place using
              mount --rbind olddir newdir

       Since  Linux  2.5.1  it  is  possible  to  atomically move a subtree to
       another place. The call is
              mount --move olddir newdir

       The proc file system is not associated with a special device, and  when
       mounting  it, an arbitrary keyword, such as proc can be used instead of
       a device specification.  (The customary choice none is less  fortunate:
       the error message `none busy' from umount can be confusing.)

       Most  devices are indicated by a file name (of a block special device),
       like /dev/sda1, but there are other possibilities. For example, in  the
       case  of  an  NFS mount, device may look like knuth.cwi.nl:/dir.  It is
       possible to indicate a block special device using its volume  label  or
       UUID (see the -L and -U options below).

       The  file  /etc/fstab (see fstab(5)), may contain lines describing what
       devices are usually mounted where, using which options.  This  file  is
       used in three ways:

       (i) The command
              mount -a [-t type] [-O optlist]
       (usually  given  in  a bootscript) causes all file systems mentioned in
       fstab (of the proper type  and/or  having  or  not  having  the  proper
       options)  to  be mounted as indicated, except for those whose line con-
       tains the noauto keyword. Adding the -F option will make mount fork, so
       that the filesystems are mounted simultaneously.

       (ii)  When  mounting  a  file system mentioned in fstab, it suffices to
       give only the device, or only the mount point.

       (iii) Normally, only the superuser can mount  file  systems.   However,
       when  fstab  contains the user option on a line, then anybody can mount
       the corresponding system.

       Thus, given a line
              /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide
       any user can mount the iso9660 file system found on his CDROM using the
       command
              mount /dev/cdrom
       or
              mount /cd
       For  more details, see fstab(5).  Only the user that mounted a filesys-
       tem can unmount it again.  If any user should be able to unmount,  then
       use users instead of user in the fstab line.  The owner option is simi-
       lar to the user option, with the restriction that the user must be  the
       owner  of  the  special  file. This may be useful e.g. for /dev/fd if a
       login script makes the console user owner of this device.

       The programs mount and umount maintain a list of currently mounted file
       systems  in  the  file  /etc/mtab.  If no arguments are given to mount,
       this list is printed.  When the proc  filesystem  is  mounted  (say  at
       /proc),  the  files  /etc/mtab  and /proc/mounts have very similar con-
       tents. The former has somewhat more  information,  such  as  the  mount
       options  used,  but  is  not  necessarily up-to-date (cf. the -n option
       below). It is possible to replace  /etc/mtab  by  a  symbolic  link  to
       /proc/mounts,  but some information is lost that way, and in particular
       working with the loop device will be less convenient.


OPTIONS
       The full set of options used by an invocation of mount is determined by
       first  extracting the options for the file system from the fstab table,
       then applying any options specified by the  -o  argument,  and  finally
       applying a -r or -w option, when present.

       Options available for the mount command:

       -V     Output version.

       -h     Print a help message.

       -v     Verbose mode.

       -a     Mount all filesystems (of the given types) mentioned in fstab.

       -F     (Used  in  conjunction  with -a.)  Fork off a new incarnation of
              mount for each device.  This will do  the  mounts  on  different
              devices  or  different  NFS  servers  in parallel.  This has the
              advantage that it is faster; also NFS timeouts go in parallel. A
              disadvantage  is  that  the  mounts are done in undefined order.
              Thus, you cannot use this option if you want to mount both  /usr
              and /usr/spool.

       -f     Causes  everything to be done except for the actual system call;
              if it's not obvious, this ``fakes'' mounting  the  file  system.
              This  option is useful in conjunction with the -v flag to deter-
              mine what the mount command is trying to do. It can also be used
              to add entries for devices that were mounted earlier with the -n
              option.

       -l     Add the ext2, ext3 and XFS labels in  the  mount  output.  Mount
              must have permission to read the disk device (e.g. be suid root)
              for this to work.  One can set such a label  for  ext2  or  ext3
              using the e2label(8) utility, or for XFS using xfs_admin(8).

       -n     Mount without writing in /etc/mtab.  This is necessary for exam-
              ple when /etc is on a read-only file system.

       -s     Tolerate sloppy mount options rather  than  failing.  This  will
              ignore mount options not supported by a filesystem type. Not all
              filesystems support this option. This option exists for  support
              of the Linux autofs-based automounter.

       -r     Mount the file system read-only. A synonym is -o ro.

       -w     Mount the file system read/write. This is the default. A synonym
              is -o rw.

       -L label
              Mount the partition that has the specified label.

       -U uuid
              Mount the partition that has  the  specified  uuid.   These  two
              options  require  the file /proc/partitions (present since Linux
              2.1.116) to exist.

       -t vfstype
              The argument following the -t is used to indicate the file  sys-
              tem  type.   The file system types which are currently supported
              are: adfs, affs, autofs, coda, coherent,  cramfs,  devpts,  efs,
              ext,  ext2,  ext3, hfs, hpfs, iso9660, jfs, minix, msdos, ncpfs,
              nfs, ntfs, proc, qnx4,  ramfs,  reiserfs,  romfs,  smbfs,  sysv,
              tmpfs,  udf,  ufs,  umsdos,  vfat, xenix, xfs, xiafs.  Note that
              coherent, sysv and xenix  are  equivalent  and  that  xenix  and
              coherent  will be removed at some point in the future  use sysv
              instead. Since kernel version 2.1.21 the types ext and xiafs  do
              not exist anymore.

              For most types all the mount program has to do is issue a simple
              mount(2) system call, and no detailed knowledge of the  filesys-
              tem type is required.  For a few types however (like nfs, smbfs,
              ncpfs) ad hoc code is necessary. The nfs ad hoc  code  is  built
              in,  but smbfs and ncpfs have a separate mount program. In order
              to make it possible to treat all types in a uniform  way,  mount
              will  execute the program /sbin/mount.TYPE (if that exists) when
              called with type TYPE.  Since various versions of  the  smbmount
              program  have different calling conventions, /sbin/mount.smb may
              have to be a shell script that sets up the desired call.

              The type iso9660 is the default.  If no -t option is  given,  or
              if  the auto type is specified, the superblock is probed for the
              filesystem type (adfs, bfs, cramfs, ext, ext2, ext3, hfs,  hpfs,
              iso9660,  jfs,  minix,  ntfs,  qnx4,  reiserfs, romfs, udf, ufs,
              vxfs, xfs, xiafs are supported).  If  this  probe  fails,  mount
              will try to read the file /etc/filesystems, or, if that does not
              exist, /proc/filesystems.  All of the  filesystem  types  listed
              there  will  be tried, except for those that are labeled "nodev"
              (e.g., devpts, proc and nfs).  If  /etc/filesystems  ends  in  a
              line  with  a  single  * only, mount will read /proc/filesystems
              afterwards.

              The auto type may be useful for user-mounted floppies.  Creating
              a  file /etc/filesystems can be useful to change the probe order
              (e.g., to try vfat before msdos) or if you use a  kernel  module
              autoloader.  Warning: the probing uses a heuristic (the presence
              of appropriate `magic'), and could recognize the wrong  filesys-
              tem  type, possibly with catastrophic consequences. If your data
              is valuable, don't ask mount to guess.

              More than one type may be specified in a comma  separated  list.
              The list of file system types can be prefixed with no to specify
              the file system types on which no action should be taken.  (This
              can be meaningful with the -a option.)

              For example, the command:
                     mount -a -t nomsdos,ext
              mounts all file systems except those of type msdos and ext.

       -O     Used  in conjunction with -a, to limit the set of filesystems to
              which the -a is applied.  Like -t in this regard except that  it
              is  useless  except in the context of -a.  For example, the com-
              mand:
                     mount -a -O no_netdev
              mounts all file systems except those which have the option _net-
              dev specified in the options field in the /etc/fstab file.

              It  is different from -t in that each option is matched exactly;
              a leading no at the beginning of one option does not negate  the
              rest.

              The  -t  and  -O  options are cumulative in effect; that is, the
              command
                     mount -a -t ext2 -O _netdev
              mounts all ext2 filesystems with the  _netdev  option,  not  all
              filesystems  that  are  either  ext2  or have the _netdev option
              specified.

       -o     Options are specified with a -o flag followed by a  comma  sepa-
              rated  string of options.  Some of these options are only useful
              when they appear in the /etc/fstab file.  The following  options
              apply  to  any  file system that is being mounted (but not every
              file system actually honors them - e.g., the sync  option  today
              has effect only for ext2, ext3 and ufs):

              async  All I/O to the file system should be done asynchronously.

              atime  Update inode access time for each  access.  This  is  the
                     default.

              auto   Can be mounted with the -a option.

              defaults
                     Use  default  options: rw, suid, dev, exec, auto, nouser,
                     and async.

              dev    Interpret character or block special devices on the  file
                     system.

              exec   Permit execution of binaries.

              _netdev
                     The  filesystem resides on a device that requires network
                     access (used to prevent the  system  from  attempting  to
                     mount  these  filesystems  until  the  network  has  been
                     enabled on the system).

              noatime
                     Do not update inode access  times  on  this  file  system
                     (e.g,  for  faster  access  on the news spool to speed up
                     news servers).

              noauto Can only be mounted explicitly (i.e., the -a option  will
                     not cause the file system to be mounted).

              nodev  Do  not  interpret  character or block special devices on
                     the file system.

              noexec Do not allow execution of any  binaries  on  the  mounted
                     file  system.   This  option might be useful for a server
                     that has file systems containing binaries  for  architec-
                     tures other than its own.

              nosuid Do  not allow set-user-identifier or set-group-identifier
                     bits to take effect. (This seems safe,  but  is  in  fact
                     rather unsafe if you have suidperl(1) installed.)

              nouser Forbid  an  ordinary  (i.e.,  non-root) user to mount the
                     file system.  This is the default.

              remount
                     Attempt to remount an already-mounted file system.   This
                     is  commonly  used  to  change the mount flags for a file
                     system, especially to make a readonly file system  write-
                     able. It does not change device or mount point.

              ro     Mount the file system read-only.

              rw     Mount the file system read-write.

              suid   Allow set-user-identifier or set-group-identifier bits to
                     take effect.

              sync   All I/O to the file system should be done  synchronously.

              dirsync
                     All  directory  updates  within the file system should be
                     done synchronously.  This affects  the  following  system
                     calls:  creat, link, unlink, symlink, mkdir, rmdir, mknod
                     and rename.

              user   Allow an ordinary user to mount  the  file  system.   The
                     name  of  the mounting user is written to mtab so that he
                     can unmount the file system again.  This  option  implies
                     the  options noexec, nosuid, and nodev (unless overridden
                     by  subsequent   options,   as   in   the   option   line
                     user,exec,dev,suid).

              users  Allow  every  user  to mount and unmount the file system.
                     This option implies the options noexec, nosuid, and nodev
                     (unless  overridden  by  subsequent  options,  as  in the
                     option line users,exec,dev,suid).

       --bind Remount a subtree somewhere  else  (so  that  its  contents  are
              available in both places). See above.

       --move Move a subtree to some other place. See above.


FILESYSTEM SPECIFIC MOUNT OPTIONS
       The following options apply only to certain file systems.  We sort them
       by file system. They all follow the -o flag.

Mount options for adfs
       uid=value and gid=value
              Set the owner  and  group  of  the  files  in  the  file  system
              (default: uid=gid=0).

       ownmask=value and othmask=value
              Set the permission mask for ADFS 'owner' permissions and 'other'
              permissions,  respectively  (default:  0700  and  0077,  respec-
              tively).     See    also   /usr/src/linux/Documentation/filesys-
              tems/adfs.txt.

Mount options for affs
       uid=value and gid=value
              Set the owner and group of the root of the file system (default:
              uid=gid=0,  but  with option uid or gid without specified value,
              the uid and gid of the current process are taken).

       setuid=value and setgid=value
              Set the owner and group of all files.

       mode=value
              Set the mode of all files to value & 0777 disregarding the orig-
              inal  permissions.   Add  search  permission to directories that
              have read permission.  The value is given in octal.

       protect
              Do not allow any changes to the protection bits on the file sys-
              tem.

       usemp  Set  uid  and  gid of the root of the file system to the uid and
              gid of the mount point upon the first sync or umount,  and  then
              clear this option. Strange...

       verbose
              Print an informational message for each successful mount.

       prefix=string
              Prefix used before volume name, when following a link.

       volume=string
              Prefix  (of  length at most 30) used before '/' when following a
              symbolic link.

       reserved=value
              (Default: 2.) Number of  unused  blocks  at  the  start  of  the
              device.

       root=value
              Give explicitly the location of the root block.

       bs=value
              Give blocksize. Allowed values are 512, 1024, 2048, 4096.

       grpquota / noquota / quota / usrquota
              These  options are accepted but ignored.  (However, quota utili-
              ties may react to such strings in /etc/fstab.)


Mount options for coherent
       None.


Mount options for devpts
       The devpts file system is a pseudo file system,  traditionally  mounted
       on  /dev/pts.   In  order to acquire a pseudo terminal, a process opens
       /dev/ptmx; the number of the pseudo terminal is then made available  to
       the   process  and  the  pseudo  terminal  slave  can  be  accessed  as
       /dev/pts/<number>.

       uid=value and gid=value
              This sets the owner or the group of newly created  PTYs  to  the
              specified values. When nothing is specified, they will be set to
              the UID and GID of the creating process.  For example, if  there
              is  a  tty group with GID 5, then gid=5 will cause newly created
              PTYs to belong to the tty group.

       mode=value
              Set the mode of newly created PTYs to the specified value.   The
              default  is  0600.  A value of mode=620 and gid=5 makes "mesg y"
              the default on newly created PTYs.


Mount options for ext
       None.  Note that the `ext' file  system  is  obsolete.  Don't  use  it.
       Since  Linux  version  2.1.21  extfs  is  no  longer part of the kernel
       source.


Mount options for ext2
       The `ext2' file system is the standard Linux file  system.   Due  to  a
       kernel bug, it may be mounted with random mount options (fixed in Linux
       2.0.4).

       bsddf / minixdf
              Set the behaviour  for  the  statfs  system  call.  The  minixdf
              behaviour is to return in the f_blocks field the total number of
              blocks of the file system, while the bsddf behaviour  (which  is
              the default) is to subtract the overhead blocks used by the ext2
              file system and not available for file storage. Thus

       % mount /k -o minixdf; df /k; umount /k
       Filesystem   1024-blocks  Used Available Capacity Mounted on
       /dev/sda6      2630655   86954  2412169      3%   /k
       % mount /k -o bsddf; df /k; umount /k
       Filesystem   1024-blocks  Used Available Capacity Mounted on
       /dev/sda6      2543714      13  2412169      0%   /k

       (Note that this example shows that one can add command line options  to
       the options given in /etc/fstab.)


       check / check=normal / check=strict
              Set  checking  level.  When at least one of these options is set
              (and check=normal is set  by  default)  the  inodes  and  blocks
              bitmaps  are checked upon mount (which can take half a minute or
              so on a big disk, and is rather useless).  With strict checking,
              block  deallocation checks that the block to free is in the data
              zone.

       check=none / nocheck
              No checking is done. This is fast. Recent kernels do not have  a
              check  option anymore - checking with e2fsck(8) is more meaning-
              ful.

       debug  Print debugging info upon each (re)mount.

       errors=continue / errors=remount-ro / errors=panic
              Define the behaviour when  an  error  is  encountered.   (Either
              ignore  errors  and just mark the file system erroneous and con-
              tinue, or remount the file system read-only, or panic  and  halt
              the  system.)   The default is set in the filesystem superblock,
              and can be changed using tune2fs(8).

       grpid or bsdgroups / nogrpid or sysvgroups
              These options define what group id a newly  created  file  gets.
              When  grpid  is  set,  it takes the group id of the directory in
              which it is created; otherwise (the default) it takes the  fsgid
              of  the current process, unless the directory has the setgid bit
              set, in which case it takes the gid from the  parent  directory,
              and also gets the setgid bit set if it is a directory itself.

       resgid=n and resuid=n
              The ext2 file system reserves a certain percentage of the avail-
              able space (by default 5%, see mke2fs(8) and tune2fs(8)).  These
              options  determine  who  can use the reserved blocks.  (Roughly:
              whoever has the specified  uid,  or  belongs  to  the  specified
              group.)

       sb=n   Instead  of  block  1,  use block n as superblock. This could be
              useful when the filesystem has been damaged.   (Earlier,  copies
              of  the  superblock would be made every 8192 blocks: in block 1,
              8193, 16385, ... (and one got  hundreds  or  even  thousands  of
              copies on a big filesystem). Since version 1.08, mke2fs has a -s
              (sparse superblock)  option  to  reduce  the  number  of  backup
              superblocks,  and  since  version 1.15 this is the default. Note
              that this may mean that ext2 filesystems  created  by  a  recent
              mke2fs cannot be mounted r/w under Linux 2.0.*.)  The block num-
              ber here uses 1k units. Thus, if you want to use  logical  block
              32768 on a filesystem with 4k blocks, use "sb=131072".

       grpquota / noquota / quota / usrquota
              These options are accepted but ignored.


       nouid32
              Disables  32-bit  UIDs  and  GIDs.  This is for interoperability
              with older kernels which only store and expect 16-bit values.



Mount options for ext3
       The `ext3' file system is version of the ext2  file  system  which  has
       been  enhanced  with journalling.  It supports the same options as ext2
       as well as the following additions:

       journal=update
              Update the ext3 file system's journal to the current format.

       journal=inum
              When a journal already exists, this option  is  ignored.  Other-
              wise,  it specifies the number of the inode which will represent
              the ext3 file system's journal file;  ext3  will  create  a  new
              journal,  overwriting  the  old contents of the file whose inode
              number is inum.

       noload Do not load the ext3 file system's journal on mounting.

       data=journal / data=ordered / data=writeback
              Specifies the journalling  mode  for  file  data.   Metadata  is
              always journaled.

              journal
                     All  data  is  committed  into the journal prior to being
                     written into the main file system.

              ordered
                     This is the default mode.  All data  is  forced  directly
                     out  to  the main file system prior to its metadata being
                     committed to the journal.

              writeback
                     Data ordering is not preserved - data may be written into
                     the  main file system after its metadata has been commit-
                     ted to the journal.  This is rumoured to be the  highest-
                     throughput  option.   It  guarantees internal file system
                     integrity, however it can allow old  data  to  appear  in
                     files after a crash and journal recovery.


Mount options for fat
       (Note:  fat  is  not  a  separate  filesystem, but a common part of the
       msdos, umsdos and vfat filesystems.)

       blocksize=512 / blocksize=1024 / blocksize=2048
              Set blocksize (default 512).

       uid=value and gid=value
              Set the owner and group of all files. (Default: the uid and  gid
              of the current process.)

       umask=value
              Set  the  umask  (the  bitmask  of  the permissions that are not
              present). The default is the umask of the current process.   The
              value is given in octal.

       dmask=value
              Set  the  umask applied to directories only.  The default is the
              umask of the current process.  The  value  is  given  in  octal.
              Present since 2.5.43.

       fmask=value
              Set the umask applied to regular files only.  The default is the
              umask of the current process.  The  value  is  given  in  octal.
              Present since 2.5.43.

       check=value
              Three different levels of pickyness can be chosen:

              r[elaxed]
                     Upper  and  lower  case are accepted and equivalent, long
                     name  parts  are  truncated  (e.g.    verylongname.foobar
                     becomes  verylong.foo),  leading  and embedded spaces are
                     accepted in each name part (name and extension).

              n[ormal]
                     Like "relaxed", but many special  characters  (*,  ?,  <,
                     spaces, etc.) are rejected.  This is the default.

              s[trict]
                     Like  "normal",  but names may not contain long parts and
                     special characters that are sometimes used on Linux,  but
                     are  not  accepted by MS-DOS are rejected. (+, =, spaces,
                     etc.)

       codepage=value
              Sets the codepage for converting to shortname characters on  FAT
              and VFAT filesystems. By default, codepage 437 is used.

       conv=b[inary] / conv=t[ext] / conv=a[uto]
              The  fat  file system can perform CRLF<-->NL (MS-DOS text format
              to UNIX text format) conversion in  the  kernel.  The  following
              conversion modes are available:

              binary no translation is performed.  This is the default.

              text   CRLF<-->NL translation is performed on all files.

              auto   CRLF<-->NL  translation  is  performed  on all files that
                     don't have a "well-known binary" extension. The  list  of
                     known  extensions  can  be  found  at  the  beginning  of
                     fs/fat/misc.c (as of 2.0, the list  is:  exe,  com,  bin,
                     app,  sys,  drv,  ovl, ovr, obj, lib, dll, pif, arc, zip,
                     lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,  gz,  tgz,
                     deb,  gif,  bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,
                     dvi).

              Programs that do computed lseeks won't like in-kernel text  con-
              version.   Several  people  have  had  their data ruined by this
              translation. Beware!

              For file systems mounted  in  binary  mode,  a  conversion  tool
              (fromdos/todos) is available.

       cvf_format=module
              Forces the driver to use the CVF (Compressed Volume File) module
              cvf_module instead of auto-detection.  If  the  kernel  supports
              kmod, the cvf_format=xxx option also controls on-demand CVF mod-
              ule loading.

       cvf_option=option
              Option passed to the CVF module.

       debug  Turn on the debug flag.  A version string and  a  list  of  file
              system  parameters  will be printed (these data are also printed
              if the parameters appear to be inconsistent).

       fat=12 / fat=16 / fat=32
              Specify a 12, 16 or 32 bit fat.  This  overrides  the  automatic
              FAT type detection routine.  Use with caution!

       iocharset=value
              Character set to use for converting between 8 bit characters and
              16 bit Unicode characters. The default is iso8859-1.  Long file-
              names are stored on disk in Unicode format.

       quiet  Turn on the quiet flag.  Attempts to chown or chmod files do not
              return errors, although they fail. Use with caution!

       sys_immutable, showexec, dots, nodots, dotsOK=[yes|no]
              Various misguided attempts to force Unix or DOS conventions onto
              a FAT file system.


Mount options for hpfs
       uid=value and gid=value
              Set  the owner and group of all files. (Default: the uid and gid
              of the current process.)

       umask=value
              Set the umask (the bitmask  of  the  permissions  that  are  not
              present).  The default is the umask of the current process.  The
              value is given in octal.

       case=lower / case=asis
              Convert all files names to lower case, or leave them.  (Default:
              case=lower.)

       conv=binary / conv=text / conv=auto
              For  conv=text,  delete some random CRs (in particular, all fol-
              lowed by NL) when reading a file.  For conv=auto, choose more or
              less   at   random   between  conv=binary  and  conv=text.   For
              conv=binary, just read what is in the file. This is the default.

       nocheck
              Do not abort mounting when certain consistency checks fail.


Mount options for iso9660
       ISO  9660 is a standard describing a filesystem structure to be used on
       CD-ROMs. (This filesystem type is also seen on some DVDs. See also  the
       udf filesystem.)

       Normal  iso9660  filenames  appear  in  a  8.3  format  (i.e., DOS-like
       restrictions on filename length), and in addition all characters are in
       upper  case.   Also  there  is no field for file ownership, protection,
       number of links, provision for block/character devices, etc.

       Rock Ridge is an extension to iso9660 that provides all of  these  unix
       like features.  Basically there are extensions to each directory record
       that supply all of the additional information, and when Rock  Ridge  is
       in  use,  the  filesystem  is indistinguishable from a normal UNIX file
       system (except that it is read-only, of course).

       norock Disable the use of Rock Ridge extensions, even if available. Cf.
              map.

       nojoliet
              Disable  the  use of Microsoft Joliet extensions, even if avail-
              able. Cf. map.

       check=r[elaxed] / check=s[trict]
              With check=relaxed, a filename is first converted to lower  case
              before  doing  the  lookup.   This  is  probably only meaningful
              together with norock and map=normal.  (Default: check=strict.)

       uid=value and gid=value
              Give all files in the file system the indicated  user  or  group
              id,  possibly overriding the information found in the Rock Ridge
              extensions.  (Default: uid=0,gid=0.)

       map=n[ormal] / map=o[ff] / map=a[corn]
              For non-Rock Ridge volumes, normal name translation  maps  upper
              to  lower case ASCII, drops a trailing `;1', and converts `;' to
              `.'.  With map=off no name  translation  is  done.  See  norock.
              (Default:  map=normal.)   map=acorn  is like map=normal but also
              apply Acorn extensions if present.

       mode=value
              For non-Rock Ridge volumes, give all files the  indicated  mode.
              (Default:  read  permission  for everybody.)  Since Linux 2.1.37
              one no longer needs to specify the mode in  decimal.  (Octal  is
              indicated by a leading 0.)

       unhide Also show hidden and associated files.

       block=[512|1024|2048]
              Set   the   block   size  to  the  indicated  value.   (Default:
              block=1024.)

       conv=a[uto] / conv=b[inary] / conv=m[text] / conv=t[ext]
              (Default: conv=binary.)  Since Linux 1.3.54 this option  has  no
              effect  anymore.   (And non-binary settings used to be very dan-
              gerous, possibly leading to silent data corruption.)

       cruft  If the high byte of the file length contains other garbage,  set
              this  mount  option  to  ignore  the high order bits of the file
              length.  This implies that a file cannot be  larger  than  16MB.
              The  `cruft' option is set automatically if the entire CDROM has
              a weird size (negative, or more than 800MB). It is also set when
              volume sequence numbers other than 0 or 1 are seen.

       session=x
              Select number of session on multisession CD. (Since 2.3.4.)

       sbsector=xxx
              Session begins from sector xxx. (Since 2.3.4.)


Mount options for minix
       None.


Mount options for msdos
       See  mount options for fat.  If the msdos file system detects an incon-
       sistency, it reports an error and sets the file system  read-only.  The
       file system can be made writeable again by remounting it.


Mount options for ncp
       Just  like  nfs,  the  ncp  implementation expects a binary argument (a
       struct ncp_mount_data) to the mount system call. This argument is  con-
       structed  by  ncpmount(8)  and the current version of mount (2.6h) does
       not know anything about ncp.


Mount options for nfs
       Instead of a textual option string, parsed by the kernel, the nfs  file
       system  expects  a  binary argument of type struct nfs_mount_data.  The
       program  mount  itself  parses  the  following  options  of  the   form
       `tag=value',  and  puts  them  in  the  structure  mentioned:  rsize=n,
       wsize=n,  timeo=n,  retrans=n,  acregmin=n,   acregmax=n,   acdirmin=n,
       acdirmax=n,  actimeo=n,  retry=n,  port=n, mountport=n, mounthost=name,
       mountprog=n, mountvers=n, nfsprog=n, nfsvers=n, namlen=n.   The  option
       addr=n  is  accepted  but ignored.  Also the following Boolean options,
       possibly preceded by no are  recognized:  bg,  fg,  soft,  hard,  intr,
       posix, cto, ac, tcp, udp, lock.  For details, see nfs(5).

       Especially useful options include

       rsize=8192,wsize=8192
              This  will make your nfs connection faster than with the default
              buffer size of 4096. (NFSv2 does not work with larger values  of
              rsize and wsize.)

       hard   The  program  accessing a file on a NFS mounted file system will
              hang when the server crashes. The process cannot be  interrupted
              or  killed unless you also specify intr.  When the NFS server is
              back online the program will continue undisturbed from where  it
              was. This is probably what you want.

       soft   This  option  allows the kernel to time out if the nfs server is
              not responding for some time. The time  can  be  specified  with
              timeo=time.   This  option  might  be  useful if your nfs server
              sometimes doesn't respond or will be rebooted while some process
              tries  to  get  a  file from the server.  Usually it just causes
              lots of trouble.

       nolock Do not use locking. Do not start lockd.


Mount options for ntfs
       iocharset=name
              Character set to use when returning file  names.   Unlike  VFAT,
              NTFS suppresses names that contain unconvertible characters.

       utf8   Use UTF-8 for converting file names.

       uni_xlate=[0|1|2]
              For  0  (or  `no'  or  `false'), do not use escape sequences for
              unknown Unicode characters.  For 1 (or `yes' or  `true')  or  2,
              use vfat-style 4-byte escape sequences starting with ":". Here 2
              give a little-endian encoding  and  1  a  byteswapped  bigendian
              encoding.

       posix=[0|1]
              If  enabled  (posix=1),  the  file  system distinguishes between
              upper and lower case. The 8.3 alias names are presented as  hard
              links instead of being suppressed.

       uid=value, gid=value and umask=value
              Set  the  file permission on the filesystem.  The umask value is
              given in octal.  By default, the files are owned by root and not
              readable by somebody else.


Mount options for proc
       uid=value and gid=value
              These options are recognized, but have no effect as far as I can
              see.


Mount options for ramfs
       Ramfs is a memory based filesystem. Mount it and you have  it.  Unmount
       it  and it is gone. Present since Linux 2.3.99pre4.  There are no mount
       options.


Mount options for reiserfs
       Reiserfs is a journaling filesystem.  The reiserfs  mount  options  are
       more fully described at http://www.namesys.com/mount-options.html.

       conv   Instructs  version  3.6 reiserfs software to mount a version 3.5
              file system, using the 3.6 format  for  newly  created  objects.
              This  file system will no longer be compatible with reiserfs 3.5
              tools.

       hash=rupasov / hash=tea / hash=r5 / hash=detect
              Choose which hash function  reiserfs  will  use  to  find  files
              within directories.

              rupasov
                     A hash invented by Yury Yu. Rupasov.  It is fast and pre-
                     serves locality,  mapping  lexicographically  close  file
                     names  to  close  hash values.  This option should not be
                     used, as it causes a high probability of hash collisions.

              tea    A    Davis-Meyer    function    implemented   by   Jeremy
                     Fitzhardinge.  It uses hash permuting bits in  the  name.
                     It  gets  high randomness and, therefore, low probability
                     of hash collisions at come CPU cost.  This may be used if
                     EHASHCOLLISION errors are experienced with the r5 hash.

              r5     A  modified  version  of  the rupasov hash. It is used by
                     default and is the best choice unless the file system has
                     huge directories and unusual file-name patterns.

              detect Instructs  mount  to detect which hash function is in use
                     by examining the file system being mounted,  and to write
                     this  information  into  the reiserfs superblock. This is
                     only useful on the first mount of an old format file sys-
                     tem.

       hashed_relocation
              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

       no_unhashed_relocation
              Tunes the block allocator. This may provide performance improve-
              ments in some situations.

       noborder
              Disable  the  border  allocator  algorithm  invented by Yury Yu.
              Rupasov.  This may provide performance improvements in some sit-
              uations.

       nolog  Disable   journalling.  This  will  provide  slight  performance
              improvements in some situations at the cost of losing reiserfs's
              fast  recovery  from  crashes.  Even with this option turned on,
              reiserfs still performs all  journalling  operations,  save  for
              actual  writes  into  its  journalling  area.  Implementation of
              nolog is a work in progress.

       notail By  default,  reiserfs  stores  small  files  and  `file  tails'
              directly  into  its  tree.  This confuses some utilities such as
              LILO(8).  This option is used to disable packing of  files  into
              the tree.

       replayonly
              Replay  the  transactions  which  are in the journal, but do not
              actually mount the file system. Mainly used by reiserfsck.

       resize=number
              A remount option which permits online expansion of reiserfs par-
              titions.   Instructs reiserfs to assume that the device has num-
              ber blocks.  This option is designed for use with devices  which
              are  under  logical volume management (LVM).  There is a special
              resizer    utility    which     can     be     obtained     from
              ftp://ftp.namesys.com/pub/reiserfsprogs.


Mount options for romfs
       None.


Mount options for smbfs
       Just  like  nfs,  the  smb  implementation expects a binary argument (a
       struct smb_mount_data) to the mount system call. This argument is  con-
       structed  by  smbmount(8)  and the current version of mount (2.9w) does
       not know anything about smb.


Mount options for sysv
       None.


Mount options for tmpfs
       The following parameters accept a suffix k, m  or  g  for  Ki,  Mi,  Gi
       (binary kilo, mega and giga) and can be changed on remount.

       size=nbytes
              Override  default  size of the filesystem.  The size is given in
              bytes, and rounded down to entire pages.  The default is half of
              the memory.

       nr_blocks=
              Set number of blocks.

       nr_inodes=
              Set number of inodes.

       mode=  Set initial permissions of the root directory.


Mount options for udf
       udf  is  the  "Universal Disk Format" filesystem defined by the Optical
       Storage Technology Association, and is often  used  for  DVD-ROM.   See
       also iso9660.

       gid=   Set the default group.

       umask= Set the default umask.  The value is given in octal.

       uid=   Set the default user.

       unhide Show otherwise hidden files.

       undelete
              Show deleted files in lists.

       strict Set strict conformance (unused).

       utf8   (unused).

       iocharset
              (unused).

       bs=    Set the block size. (May not work unless 2048.)

       novrs  Skip volume sequence recognition.

       session=
              Set the CDROM session counting from 0. Default: last session.

       anchor=
              Override standard anchor location. Default: 256.

       volume=
              Override the VolumeDesc location. (unused)

       partition=
              Override the PartitionDesc location. (unused)

       lastblock=
              Set the last block of the filesystem.

       fileset=
              Override the fileset block location. (unused)

       rootdir=
              Override the root directory location. (unused)


Mount options for ufs
       ufstype=value
              UFS is a file system widely used in different operating systems.
              The problem are differences among implementations.  Features  of
              some  implementations are undocumented, so its hard to recognize
              the type of ufs automatically.  That's why the user must specify
              the type of ufs by mount option.  Possible values are:

              old    Old  format  of  ufs,  this  is  the  default, read only.
                     (Don't forget to give the -r option.)

              44bsd  For   filesystems   created   by   a   BSD-like    system
                     (NetBSD,FreeBSD,OpenBSD).

              sun    For filesystems created by SunOS or Solaris on Sparc.

              sunx86 For filesystems created by Solaris on x86.

              nextstep
                     For  filesystems  created  by  NeXTStep (on NeXT station)
                     (currently read only).

              nextstep-cd
                     For NextStep CDROMs (block_size == 2048), read-only.

              openstep
                     For  filesystems  created  by  OpenStep  (currently  read
                     only).   The  same filesystem type is also used by Mac OS
                     X.


       onerror=value
              Set behaviour on error:

              panic  If an error is encountered, cause a kernel panic.

              [lock|umount|repair]
                     These mount options don't do anything at present; when an
                     error is encountered only a console message is printed.


Mount options for umsdos
       See mount options for msdos.  The dotsOK option is explicitly killed by
       umsdos.


Mount options for vfat
       First of all, the mount options for fat  are  recognized.   The  dotsOK
       option is explicitly killed by vfat.  Furthermore, there are

       uni_xlate
              Translate   unhandled  Unicode  characters  to  special  escaped
              sequences.  This lets you backup and restore filenames that  are
              created  with any Unicode characters. Without this option, a '?'
              is used when no translation is possible. The escape character is
              ':'  because it is otherwise illegal on the vfat filesystem. The
              escape sequence that gets used, where u is the  unicode  charac-
              ter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).

       posix  Allow two files with names that only differ in case.

       nonumtail
              First  try  to make a short name without sequence number, before
              trying name~num.ext.

       utf8   UTF8 is the filesystem safe 8-bit encoding of  Unicode  that  is
              used  by  the  console.  It can be be enabled for the filesystem
              with this option.  If `uni_xlate' gets set, UTF8 gets  disabled.

       shortname=[lower|win95|winnt|mixed]

              Defines  the  behaviour  for  creation  and display of filenames
              which fit into 8.3 characters. If a long name for a file exists,
              it will always be preferred display. There are four modes:

              lower  Force  the short name to lower case upon display; store a
                     long name when the short name is not all upper case.

              win95  Force the short name to upper case upon display; store  a
                     long name when the short name is not all upper case.

              winnt  Display  the  shortname as is; store a long name when the
                     short name is not all lower case or all upper case.

              mixed  Display the short name as is; store a long name when  the
                     short name is not all upper case.

       The default is "lower".


Mount options for xenix
       None.


Mount options for xfs
       biosize=size
              Sets  the  preferred  buffered  I/O  size (default size is 64K).
              size must be expressed as the logarithm (base2) of  the  desired
              I/O  size.   Valid  values  for  this  option are 14 through 16,
              inclusive (i.e. 16K, 32K, and 64K bytes).  On machines with a 4K
              pagesize,  13  (8K  bytes)  is also a valid size.  The preferred
              buffered I/O size can also be  altered  on  an  individual  file
              basis using the ioctl(2) system call.

       dmapi  /  xdsm
              Enable the DMAPI (Data Management API) event callouts.

       logbufs=value
              Set  the  number  of in-memory log buffers.  Valid numbers range
              from 2-8 inclusive.  The default value is 8 buffers for filesys-
              tems  with  a blocksize of 64K, 4 buffers for filesystems with a
              blocksize of 32K, 3 buffers for filesystems with a blocksize  of
              16K, and 2 buffers for all other configurations.  Increasing the
              number of buffers may increase performance on some workloads  at
              the  cost  of the memory used for the additional log buffers and
              their associated control structures.

       logbsize=value
              Set the size of each in-memory  log  buffer.   Valid  sizes  are
              16384  (16K)  and  32768  (32K).  The default value for machines
              with more than 32MB of memory is 32768, machines with less  mem-
              ory use 16384 by default.

       logdev=device and rtdev=device
              Use  an external log (metadata journal) and/or real-time device.
              An XFS filesystem has up to three parts: a data section,  a  log
              section,  and  a  real-time  section.   The real-time section is
              optional, and the log section can be separate from the data sec-
              tion or contained within it.  Refer to xfs(5).

       noalign
              Data  allocations will not be aligned at stripe unit boundaries.

       noatime
              Access timestamps are not updated when a file is read.

       norecovery
              The filesystem will be mounted without running log recovery.  If
              the  filesystem  was  not  cleanly unmounted, it is likely to be
              inconsistent when mounted in norecovery  mode.   Some  files  or
              directories  may not be accessible because of this.  Filesystems
              mounted norecovery must be mounted read-only or the  mount  will
              fail.

       osyncisdsync
              Make  writes  to files opened with the O_SYNC flag set behave as
              if the O_DSYNC flag had been used instead.  This can  result  in
              better performance without compromising data safety.  However if
              this option is in effect, timestamp updates from  O_SYNC  writes
              can be lost if the system crashes.

       quota / usrquota / uqnoenforce
              User  disk  quota  accounting  enabled,  and limits (optionally)
              enforced.

       grpquota / gqnoenforce
              Group disk quota  accounting  enabled  and  limits  (optionally)
              enforced.

       sunit=value and swidth=value
              Used to specify the stripe unit and width for a RAID device or a
              stripe volume.  value must be specified in 512-byte block units.
              If this option is not specified and the filesystem was made on a
              stripe volume or the stripe width or unit were specified for the
              RAID  device  at  mkfs  time,  then  the  mount system call will
              restore the value from the superblock.  For filesystems that are
              made  directly  on  RAID  devices,  these options can be used to
              override the information in the  superblock  if  the  underlying
              disk  layout changes after the filesystem has been created.  The
              swidth option is required if the sunit option  has  been  speci-
              fied, and must be a multiple of the sunit value.


Mount options for xiafs
       None. Although nothing is wrong with xiafs, it is not used much, and is
       not maintained. Probably one shouldn't use  it.   Since  Linux  version
       2.1.21 xiafs is no longer part of the kernel source.


THE LOOP DEVICE
       One  further possible type is a mount via the loop device. For example,
       the command

         mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024

       will set up the loop  device  /dev/loop3  to  correspond  to  the  file
       /tmp/fdimage,  and  then mount this device on /mnt.  This type of mount
       knows about three options, namely loop, offset and encryption, that are
       really  options to losetup(8).  If no explicit loop device is mentioned
       (but just an option `-o loop' is given), then mount will  try  to  find
       some  unused  loop device and use that.  If you are not so unwise as to
       make /etc/mtab a symbolic link to /proc/mounts  then  any  loop  device
       allocated  by  mount will be freed by umount.  You can also free a loop
       device by hand, using `losetup -d', see losetup(8).


RETURN CODES
       mount has the following return codes (the bits can be ORed):

       0      success

       1      incorrect invocation or permissions

       2      system error (out of memory, cannot fork, no more loop devices)

       4      internal mount bug or missing nfs support in mount

       8      user interrupt

       16     problems writing or locking /etc/mtab

       32     mount failure

       64     some mount succeeded


FILES
       /etc/fstab file system table
       /etc/mtab table of mounted file systems
       /etc/mtab~ lock file
       /etc/mtab.tmp temporary file

SEE ALSO
       mount(2), umount(2), fstab(5), umount(8),  swapon(8),  nfs(5),  xfs(5),
       e2label(8),  xfs_admin(8),  mountd(8),  nfsd(8), mke2fs(8), tune2fs(8),
       losetup(8)

BUGS
       It is possible for a corrupted file system to cause a crash.

       Some Linux file systems don't support -o sync and -o dirsync (the  ext2
       and  ext3  file  systems do support synchronous updates (a la BSD) when
       mounted with the sync option).

       The -o remount may not be able to change mount parameters (all  ext2fs-
       specific  parameters,  except  sb,  are  changeable with a remount, for
       example, but you can't change gid or umask for the fatfs).

HISTORY
       A mount command existed in Version 5 AT&T UNIX.



Linux 2.0                      14 September 1997                      MOUNT(8)